Presented is a discussion of an hypothesized analytical explanation of ductile fracture initiation, propagation, and arrest in cylindrical pressure vessels and piping. The hypothesized analytical treatment is an attempt to predict initiation and arrest conditions for ductile fractures using Charpy V-notch plateau energy as a means of determining the toughness of the material. Data from a number of full-scale experiments on gas transmission pipe, nuclear reactor piping, and other cylindrical vessels are presented and are shown to be in agreement with the hypothesis.